261. Hyperthermia properties of gold fiducial markers

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Abstracts / Physica Medica 56 (2018) 133–278

Table 1 Indicator

Topic

Type of Numerator indicator

Denominator

1. Equipment

Kind of hyperthermia equipment (superficial/deephyperthermia) Quality assurancy (QA)

structure Number of hyperthermia equipment

Total number of At least 1 for equipment radiotherapy machines

2. Quality control equipment

structure Number of test equipment Total number of the performed before patient treatment treated patients with hyperthermia structure Total number of patients treated in Number of workers: 1year (1) technician (2) physician (3) physicist (4) nurse Process Number of patient enrolled in Total number of clinical protocol for hyperthermia treated patients

Standard

To be checked at least once a year

At least 1 person for each figure (also part-time)

1year, repeated every 2years

100%:the standard proposed is the average percentage value considering the centers data 80%

1year, every two years

1year, or at least 6months; repeated every 2 years To be checked at least once before a new treatment Six months every 2years

Human resources productivity

4. Approved protocols

Quality improvement of patient management

5. multidisciplinary work

Process

Number of patients discussed in multidisciplinary meeting

Total number of treated patients

6. Input image (TC, eco,RM,PET)

Multidisciplinary approach to patient care Information accuracy

Process

Total number of treated patients

15%

7. Temperature measurement

Hyperthermia treatment accuracy

Process

Hyperthermia treatment control

Process

9. Thermal Dose Calculation

Quality Process improvement of hyperthermia treatment Outcome Quality improvement of patient management Treatment outcome compliance

Total number of hyperthermia treatment Total number of hyperthermia treatments Total number of hyperthermia treatments

100%: each plan should be checked during treatment

8. Treatment planning

Number of patients undergoing hyperthermia treatment receiving multi- parametric imaging (TC/eco/ RM/PET) Number of treatments in which temperature measurement is performed (yes/no) Number of hyperthermia treatment performed with treatment planning

10. Treatment outcome and toxicity 11. Patient compliance

Number of complete response (CR)/ No patients showed toxicity PG2 at 12months after the treatment Number of the patients that complete total hyperthermia treatment

evolving. The aim of this work is to propose a set of quality indicators for hyperthermia treatments in order to provide a continuous quality improvement. Methods. A preliminary set of indicators was selected on the basis of evidenced critical issues. Three structure, six process and two outcome quality indicators were obtained. A multidisciplinary team involving different professional profiles as Radiation Oncologist, Medical Physicist and Radiation Technologists, was assembled in order to underline main critical issues in the use of hyperthermia. Results. A set of 11 indicators has been developed. For each indicator, topic, type of indicator, numerator (parameter value),denominator (reference population), standard (reference value), time period for data collection and frequency of analysis have been proposed. Numerical values for the standard were selected from the international literature, when available, and from guidelines on hyperthermia/radiotherapy, or empirically on the basis of the experience of the Italian Institutes. In the table, we reported the list of hyperthermia indicators. Conclusions. The proposed indicators are available to be investigated, in particular it will be possible to conform this type of the treatment in terms of operational procedures in order to compare different data derived from different Institutes. https://doi.org/10.1016/j.ejmp.2018.04.270

Total number of treated patients Total number of treated patients

At least 1year; every 3years

100%: each plan should be checked prior to delivery

3. workload

Number of treatments in which thermal dose calculation is performed (yes/no)

Frequency of analysis

100%: each hyperthermia course should be performed with treatment planning 100%

CR=40% (late response); Toxicity G2 (12months after the treatment): 0% 100%: total number of patients complete hyperthermia treatment

1year, repeated every 2years

1year, every year

1year, every year 1year, every 1 year

261. Hyperthermia properties of gold fiducial markers S. Gallo a, P. Arosio a, M. Avolio b, L. Bonizzoni a, M. Cobianchi b, M. Gargano a, N. Ludwig a, F. Orsini a, I. Veronese a a Dipartimento di Fisica and INSTM, Università degli Studi di Milano, Milano, Italy b Dipartimento di Fisica and INSTM, Università degli Studi di Pavia, Pavia, Italy

Purpose. The combination of Radiotherapy and Magnetic Fluid Hyperthermia (MFH) is gaining importance since it may offer new strategies for several oncological pathologies. In MFH magnetic nanoparticles are injected directly into the tumour and, under the action of an externally applied alternating magnetic field HAC, they generate an amount of heat proportional to the field. Metallic materials implanted within 40 cm from the tumour heat up during MFH treatment and are removed. The aim of this work is to investigate the hyperthermia properties of the fiducial markers employed in Image Guided Radiation Therapy (IGRT) and to study the physics mechanisms of the observed macroscopic effects. Methods and materials. Hydrogel matrix samples were prepared and used as tissue mimicking materials. Different types of gold fiducial markers used in IGRT procedures were positioned in gel samples, considering various geometric configurations simulating the actual position of the markers in the clinical practice. Hyperthermic properties of gold fiducial markers were studied varying the field ampli-

Abstracts / Physica Medica 56 (2018) 133–278

tude HAC from 7 to 17 kA/m and the frequency from 100 to 1000 kHz. During the stimulation, an optical fiber based sensor enables the measurement of the temperature in a point of the hydrogel samples. Beside these temperature measurement, a high-resolution thermal camera was used to map the temperature distribution over the samples. Results. Preliminary results attested an increase of the temperature in the gel matrices as effect of the heating of the gold fiducial markers under a suitable magnetic stimulation. Hyperthermic effects were also significant in the typical experimental conditions (2 < HAC < 15 kA/m and f = 100 kHz) employed at present in MFH clinical trials. Conclusion. The results of this study highlight the need to carefully evaluate the presence and location of gold fiducial markers in patients undergoing MFH treatments, in order to prevent damage to health tissues surrounding the lesions.

Results. The ALs and the ELVs set by the 2013/35/EU Directive were not exceeded. Conclusion. The assessment of occupational exposure to electromagnetic field around 1.5 T and 3.0 T MRI scanners is difficult because of many different EMF. Furthermore many signals and modulations are present in to VHF and VLF emission spectra, besides the use into clinical practice of different equipment and acquisition techniques. In the routine daily work activities, the respect of ALs and ELVs given by 2013/35/EU Directive is demonstrated. https://doi.org/10.1016/j.ejmp.2018.04.272

263. MRI operator exposure to static magnetic fields F. Cretti a a

https://doi.org/10.1016/j.ejmp.2018.04.271

262. Assessment of occupational exposure to electromagnetic field around 1.5 T and 3.0 T MRI scanners S. Filice a, R. Rossi a, C. Pinardi b a Servizio di Fisica Sanitaria – Azienda Ospedaliero Universitaria di Parma, Parma, Italy b Università degli Studi di Parma, Parma, Italy

Purpose. MRI uses a combination of strong Static Magnetic Field (B0 , 0 Hz), which is constantly present inside and around the MRI facility, switching gradient fields oscillating in the Very Low Frequency range (VLF, 0.3–3 KHz) and radiofrequency pulses in the Very High Frequency range (VHF, 30–300 MHz). Staff entering an MRI scanner room may experience instantaneous SMF exposure, as well as time-varying magnetic field exposure (dB/dt) at extremely low frequency, when they move through the non-uniform static magnetic field nearby the scanner. In some situations MRI staff are present inside the scanner room during image acquisition, implying the exposure to the different Electromagnetic Field (EMF). In this study we investigated the compliance of occupational exposure to MRIrelated EMF with the 2013/35/EU Directive. Methods. The personnel exposure to both dB/dt and B0 during work activity were evaluated on 1.5 T and 3.0 T clinical whole body MRI scanner by using a portable electronic dosimeter for static magnetic field (TaleteÒ Tecnorad, Italy). The dosimeters was capable of measuring B0 at 18 Hz sampling rate. The estimated values were compared with the Exposure Limit Values (ELVs) established from 2013/35/EU Directive. The electric field and magnetic field associated with VLF and VHF were measured at different positions inside the scanner room for three different acquisition technique. The measured values were compared with the Action Levels (ALs) given in 2013/35/EU Directive. For f < 100 kHz non-sinusoidal (nonmonochromatic) EMF the method of weighted peak was used.

223

A.S.S.T. Papa Giovanni XXIII, Imaging Department, Bergamo, Italy

Purpose. This work aims at assessing compliance of MRI operators work conditions with European Directive’s [1] new limits, expressed in terms of ELVs (Exposure Limit Values) and ALs (Action Levels), addressing the prevention of direct and indirect scientifically wellestablished short term effects of exposure to electro-magnetic fields in humans. Methods and materials. The static magnetic field B0 around two scanners (Magnetom Espree 1.5 T, Siemens and Discovery 750 3 T, General Electric) was spatially mapped along four straight lines – roughly representative of the operator paths in the magnet room – starting from the patient bed edge until the 0.5 mT isomagnetic border, at steps DS of 5 cm (see Fig. 1). The temporal variation of the magnetic field DB0/Dt experienced by the operator moving across the spatial gradient GS of static magnetic field was estimated as DB0 =Dt ¼ DB0 =DS  DS=Dt ¼ GS  v. GS (i.e. DB0 =DS) was calculated from measured data, whereas for the operator speed v, the value of 1.0 m/s was assumed. The maximum values estimated for DB0 =Dt for the two scanners were then converted to internal electric fields using the coefficients deduced from Glover [2]. Results. The maximum values estimated for DB0 =Dt occurred in proximity to the edge of the patient’s bed and were 3.2 and 5.9 T/s for the 1.5 T and 3 T respectively. The correspondent electric fields induced in the body of the operator are shown in Table 1. Conclusion. The highest values for DB0 =Dt were found for the 3 T magnet. The estimated electric fields induced in the operator’s body respected the European Directive’s limit for sanitary effects.

References 1. European Directive 2013/35/EU 2. Glover PM, Bowtell R. Measurement of electric fields induced in a human subject due to natural movements in static magnetic

Table 1 Maximum values estimated for Gs ; DB=Dt and the correspondent electric fields induced in the body of the operator. Scanner

Initial position

Maximum GS [mT/cm]

DB/Dt [T/s]

Conversion coefficient [(V/m)/(T/ s)] abdomen Glover (2008)

Induced electric field [V/m]

ELV [V/m] Eur Dir 35/2013

Siemens Espree 1.5 T

A

32.2

3.2

0.15

0.5

1.1 sanitary effects 1 Hz 6 f < 3 kHz

B A B

12.6 58.8 21.0

1.3 5.9 2.1

GE Discovery 3 T

0.2 0.9 0.3

0.7/f sensorial effects 1 Hz 6 f < 10 Hz